Hello,
When I upgraded my servers to dovecot 2.2.13 the monitoring tool monit started to send out warnings that it couldn't reach my imap/pop3 servers through ssl any more. The same problem didn't happen on non-ssl-connections.
According to people on the monit list this is likely a dovecot issue: https://lists.gnu.org/archive/html/monit-general/2014-06/msg00031.html Let me quote:
the root cause of the error is, that dovecot 2.2.13 closes the connection if SSL is used in response to LOGOUT command instead of sending usual response. When no SSL is enabled, dovecot responses to LOGOUT command normally. [...] According to RFC 3501 (http://tools.ietf.org/html/rfc3501), LOGOUT is any-state command, where the server MUST send response before closing the connection: http://tools.ietf.org/html/rfc3501#section-3.4
=> the problem is caused by dovecot 2.2.13 bug ... its behaviour is inconsistent (LOGOUT in non-authenticated state works per RFC requirement if no SSL is used and doesn't conform to RFC if SSL is used). It is possible that the problem is related to their DoS-attack modification, which has most probably unexpected side-effect.
Maybe this is related to the DDoS-protection measures that have been added in dovecot 2.2.13.
Would apprechiate if someone could have a look.
cu,
Hanno Böck http://hboeck.de/
mail/jabber: hanno@hboeck.de GPG: BBB51E42